Calculate a conventional 60° cutting-tap drill estimate, circular diameter from area, finished-hole tolerance limits, or cylindrical hole volume. For cutting taps, d ≈ D − 0.01299 × E × P uses percent E (75, not 0.75) and matching-unit pitch P; TPI converts to pitch first. This follows Tapmatic’s inch cutting-tap convention, approximately equivalent to its rounded metric 76.98 divisor. Forming and pipe taps need different guidance. Nearest 1/64-inch grid values are comparisons, not drill recommendations.

For conventional 60° cutting taps only. Verify the actual tap, material and drill chart; not for form taps or pipe threads.

75% is an explicit planning default, not axial engagement length or a guaranteed strength.

Hole Size Formula

The following formula and example apply to the cylindrical-volume mode. For diameter from area, d = 2√(A/π). Finished-hole limits equal nominal plus the lower and upper signed deviations.

HS = pi × hr² × hd

Variables:

  • HS is ideal cylindrical hole volume (ft³), not diameter or tap-drill size
  • hr is the hole radius (ft) 
  • hd is the hole depth (ft) 

How to Calculate Hole Size?

The following steps outline how to calculate the Hole Size.

  1. First, determine the hole radius (ft). 
  2. Next, determine the hole depth (ft). 
  3. Next, gather the formula from above = HS = pi*hr^2*hd.
  4. Finally, calculate the Hole Size.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

hole radius (ft) = 3

hole depth (ft) = 10

HS = π × 3² × 10 ≈ 282.743339 ft³. The model excludes drill-tip cones, chamfers and irregular walls.